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Richard Jernigan -> RE: ...and you thought lutherie was difficult? (May 22 2013 21:44:27)
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quote:
ORIGINAL: keith
of historical note, john harrison who built the first chronometer to be used to calculate longitude was a carpenter who built clocks out of wood. the chronometers that made him famous (H1 - H4) were metal given humidity issues at sea. for those interested about mr. harrison there was an interesting book published a few years back about the chase to find a reliable procedure for calculating longitude.
One such book is Dava Sobel's "Longitude".
I'm old enough to have begun sailing long before GPS, or any other satellite navigation system was in place. The LORAN system, with land based transmitters, was operational from the early 1940s, but its coverage of the globe was incomplete, and it required an expensive receiver, so we learned celestial navigation. You have to have a good chronometer to do celestial the normal way.
Actually, there was a way of finding the time before the chronometer became reliable. It is called the lunar method. With a sextant you measure the motion of the moon among the stars. Time can be determined accurately enough to navigate.
But the lunar method was complex and difficult, deemed to be beyond the capacity of the average mariner, so it was not widely used, perhaps not even widely known.
Joshua Slocum, the great American sailing captain, was the first to sail single handed around the world. The end of the era of the great sailing ships came during Slocum's career. He was left unemployed. Someone gave him the hulk of a sloop, which Slocum rebuilt from the keel up. After failing at fishing, he hit upon the scheme of sailing alone around the world, writing paid articles for newspapers, to repair his fortunes.
Slocum couldn't afford to have his chronometer refurbished, so he navigated by the "lunars". He had a wry sense of humor, and kept onboard an old tin alarm clock which he showed to newspaper reporters at various ports around the world, claiming that he navigated with it. At one point he claimed that his alarm clock had stopped, but functioned perfectly after he boiled it.
"The want of a chronometer for the voyage was all that now worried me. In our newfangled notions of navigation it is supposed that a mariner cannot find his way without one; and I had myself drifted into this way of thinking. My old chronometer, a good one, had been long in disuse. It would cost fifteen dollars to clean and rate it. Fifteen dollars! For sufficient reasons I left that timepiece at home, where the Dutchman left his anchor."
"At Yarmouth, too, I got my famous tin clock, the only timepiece I carried on the whole voyage. The price of it was a dollar and a half, but on account of the face being smashed the merchant let me have it for a dollar."
"Sailing Alone Around the World" by Joshua Slocum
I don't recall Slocum mentioning the lunar method in his book, though it was reliably reported that he used it on his epoch-making voyage.
RNJ
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